Diving without computers

[barth]

My computer is always in gauge mode. For planning I use my smartphone. That allows me to do multilevel diveplanning.

There are also tables in my wetnotes which I can use.

After the dive I can use my pc to check the the dive profile.

Making a diveplanning and gasplanning would take 15 sec for a REC dive and max 2 minutes for a tech dive (max depth 51 m/170 feet) for me.

I did use my divecomputer (gekko)for five years. Since I bought my uwatec TEC 2g it is in gauge mode which I'm using now for eigth years. I prefer gauge mode/bottomtimer . I have never used an computer like a shearwater perdix. But if I can use a bottomtimer or a simple dive computer I will use the bottomtimer. Plan your dive and dive your plan. Or change it and discus the new diveplan and new gas planning in your wetnotes.

I do understand that it is not easy to plan dives the way that I do. For somebody who is doing two weeks of diving in a year a dive computer would be better. If you really want to invest a lot of time in diving a bottomtimer can be the best choice. But for most divers a dive computer would be better.

 

[mattia_v]

Frankly, I'd need to read the book again and fiddle around with the table to figure out what, exactly, is appropriate. I rely on my (and my GF's) computer and generally conservative dive planning (I don't do deco, I dive within the nitrox limits, and air consumption is pretty much always the limiting factor, not NDLs), precisely because most profiles are a bit meandering. Start deep-ish, (25-30m max, usually around 20-24), start ascending at half a tank (~30 to 40 minutes in, typically), and continue the dive working up the reef a little. That's our typical Bonaire profile, in any event. Rarely does the NDL counter go anywhere lower than 40 minutes or so.

Thing is, with the holiday diving (= incidental), the tendency not to do square profile or particularly 'scheduled' multilevel dives (we go on air consumption, which will depend on factors such as current and water temp), and often repetitive dives with sometimes very short surface intervals, the computer is more 'idiot proof' and at least as safe (certainly not more dangerous) than planning using a dive table. Given the 3-8 month interval between dive sessions, I'd be re-learning every time, to a degree. And that's not super 'fun' for me. Also, it's a handy log with basic info (dive time, depth, water temp, time in/out of water, etc.) that can be used to complete the dive log at a later time. Or downloaded to a PC to view the actual depth/dive profile as a whole if I'd bother to get the computer interface dongle.

 

[Damselfish]

It's not really a matter of whether it is easy to plan dives with tables/wheels/etc, or how often someone does it. It's a matter of whether it makes any sense for a particular dive to be planned to that degree. In your typical tropical recreational diving you may have a planned max depth, know the general topology of a dive site, and perhaps a general idea where there are specific things to look for, many of which will of course move. Usually you will not know the specific route you will want to take underwater. You don't know what critters will be where, where the photo ops will be, how long you will want to spend looking at anything or for something, or know when the surprise pelagic will pay a visit and for how long. You're not going to want to be following or spending cycles modifying a detailed plan when you find a rare nudi, are observing some interesting behavior, or a giant turtle decides to hang out near you. Having as much time and flexibility as possible is how you get the most out of these sorts of dives.

 

[Diver0001]

So how many divers have been diving the old way, before computers, and still prefer it that way? I am sure everyone is planning their dive and diving their plans, but even with that as a baseline, if you only dive several easygoing vacations per year, is it worth the effort of trying to press those tiny buttons? Asking for a friend...

I learned how to dive in 1984 and at the time computers were scary, expensive and "only really useful for technical divers". Technical divers were also scary and alien to us at the time because technical diving and recreational diving were seen at the time as two completely different disciplines requiring two completely different skill sets. The idea of seeing "technical diving" as just another form of more advanced "recreational diving" is actually a fairly new development in our sport. Therefore, there are still those who see the world from the old paradigm and I think it forms their opinions about tables as well.

Getting back to the point. I made my first 650-odd dives using tables. When I took my initial technical training I also used tables because at that time technical divers were ambivalent about the use of computers. I also took my Trimix training using tables because I didn't have a Trimix computer. I think I bought my first computer in about 1997 or 1998. At the time they were already becoming fairly mainstream but the one I bought was a POS and it didn't work very well. In 2002 I bought a Suunto computer that I still have and it was the first computer that I dove with extensively. I soon stopped using tables at all. I subsequently bought another Suunto computer that had a mixed gas capability for technical Nitrox and even though the algorithm it has calculates absurd ascent lines, I still use it for technical diving today.

The reason I still use this computer is because I don't need a different one for the dives I do. I have a deep understanding of deco theory and I am able to manage my ascent without the computer telling me where to make stops along the way. That said, I make a lot of dives in the same depth range so I understand that depth range very well. The computer only tells me one thing that I need to know. The TTS (time to surface). This is perhaps typical of someone who has long experience diving without a computer and making controlled ascents without a lot of input from the computer. The TTS is, however, very relevant to me and I wouldn't be able to dive anywhere near as flexibly as I can without the computer. In answering the question you posed, I "prefer" a computer because it gives me flexibility.

I still make some dives on tables for logistical reasons while I'm training (1/2 dozen last year and a few on vacation with my daughter, who was using my computer, the year before) but on the whole I now believe (and teach) that tables are an historical curiosity but that for a modern diver a computer should be viewed as mandatory gear. I make all of my students aware of the tables but only offer to teach it to those who are interested. Of all the students I had last year, 1 asked me to show her because she had read online that you are not a "real diver" if you can't do tables.

Bringing it back to the question your friend is asking, is a computer a good investment for vacation diving? Yes. Moreover, I would consider it required for vacation diving. If you are going to dive in a group and/or follow a guide then *everyone* around you is going to have a computer and the computer allows for considerably longer bottom times than the tables do. I'll explain that if you need it but for now just accept that. This means that either you are going to need to leave to the surface early on all of your dives, meaning that you will get separated from the group (and the guide) due to the early ascent on all dives. Moreover, I assume that your vacation is not in your back-yard so if you are paying good money to be diving somewhere interesting, then it pays to get the most bottom time out of your dives that you can. A few years ago I wouldn't have seen it like this because buying a computer was still an investment but these days a (simple) diving computer doesn't cost any more than a diving watch, which you will need anyway if you are going to dive with tables.

R..

 

[boulderjohn]

Leisure Pro has some very nice analog wrist-mount depth gauges for under $100 (new), and you can get any of several watches suitable for diving for around the same price. There's less maintenance and longer life than with DCs.

So if you go to the LeisurePRo web site you can get a very nice analog depth gauge for $100 and a dive watch for about the same--a total of only $200.

Or you can go to the same site and buy a dive computer (Mares Puck) for $149.95.

A problem with DCs is that there is generally no way to simulate a dive, so aside from reading the instructions, there's no way to anticipate what the DC will do. My first 20 or so dives were shallow enough that my DC didn't ask for a safety stop. I was in the habit of doing them anyway, but was a little surprised by what the display did the first time I went deeper. I've never seen its deco display, which differs in important ways from the safety stop display, but at least I've read about it. A rented DC? I'd have no idea.

Every computer has a manual that will tell and usually show with pictures what your computer will do in those situations. The problem is that the manuals also tell you a zillion things you don't need to know. Too much information is the same as not enough information unless you know how to search for it. What you need to do is identify the few key elements you need to know and then look in the table of contents for those specific pieces of information.

 

[Bubblesong]

I learned how to dive in 1984 and at the time computers were scary, expensive and "only really useful for technical divers".

... I wouldn't be able to dive anywhere near as flexibly as I can without the computer. In answering the question you posed, I "prefer" a computer because it gives me flexibility.

I still make some dives on tables for logistical reasons while I'm training (1/2 dozen last year and a few on vacation with my daughter, who was using my computer, the year before) but on the whole I now believe (and teach) that tables are an historical curiosity but that for a modern diver a computer should be viewed as mandatory gear.

Of all the students I had last year, 1 asked me to show her because she had read online that you are not a "real diver" if you can't do tables
R..

So you have both ends of the discussion, my husband and I learned dive tables in '88, and daughter five years ago, but now daughter (17) and I have computers. (So I am going to get one for hubby too).
But for my daughter, your daughter and students are starting out with computers, will they ever have they same deep knowledge of nitrogen loading and off gassing, or just trust the computer like people trust dive masters? I have read here on SCUBAboard about divers panicking after the computer malfunctions and give them obviously false deco times. So that is the other half of my concern, even though we are definitely all going with dive computer now.

 

[dmaziuk]

One thing about dive computers is that if they Fail, as I have heard.

Regs do too, does your worse half plan on diving without one for that reason?

 

[doctormike]

Plan your dive and dive your plan.

You know, we say this so often that we just assume that it's good advice for recreational dives. But the vast majority of recreational dives are not a predictable square profile that has been done many times before. Usually, the profile is based on what is encountered on the dive - spend more time at one depth if there is something to see there, spend less time elsewhere if it's less interesting. The DM tells you that the wreck is 110 feet to the sand, 90 feet to the deck, 60 feet to the wheelhouse. You are going to come up with a precise plan ahead of time? I never know what to assume in that situation.

Why would you want to restrict your dive to some preconceived plan, assuming that you can safely monitor your gas and nitrogen loading? A simple, cheap dive computer will tell you what your ACTUAL nitrogen loading is, basing your bottom time on real data, not on a guess before the dive.

So I say, plan your dive, and then dive intelligently.

 

[jseyfert3]

But for my daughter, your daughter and students are starting out with computers, will they ever have they same deep knowledge of nitrogen loading and off gassing, or just trust the computer like people trust dive masters? I have read here on SCUBAboard about divers panicking after the computer malfunctions and give them obviously false deco times. So that is the other half of my concern, even though we are definitely all going with dive computer now.

I don't see why not. Certainly you could almost bypass learning about it, but if you put your computer in PLAN mode (one button on mine) wouldn't they wonder why it gives shorter NDL right after finishing a dive? Failing to use PLAN, a subsequent dive after short SI will have less NDL.

Talking about nitrogen loading, when I upload dives from my DC to my PC, the Suunto DM5 software shows estimated nitrogen tissue loading at any stage of the dive. Kinda cool and would be a good way to explain this to new divers. Relating to this is the benefit of a computer to log your dive profiles, so you can look at them later.

I've read a lot on here, and it seems less that people panic when a computer malfunctions and gives wrong deco info but rather they panic when they exceed NDL and don't realize what the computer is telling them to do. Or they think they will die if NDL runs out and bolt to the surface to avoid that. In any case, if you suspect malfunction comparing it to your buddy's computer or the DM's would be a good idea. Planning and training helps avoid panic.

 

[boulderjohn]

But for my daughter, your daughter and students are starting out with computers, will they ever have they same deep knowledge of nitrogen loading and off gassing, or just trust the computer like people trust dive masters?

Learning to dive tables tells you absolutely nothing about decompression theory, nitrogen loading, etc. It is likely that you were taught those things in the same session in which you learned to use tables, but they are two different things. The same lessons about nitrogen ongassing and offgassing can and should be taught with the computers as well.

Mark Powell wrote an entire book (Deco for Divers) about decompression theory, and he never showed how to use any tables.